1. Field of the Invention
The present invention relates to a post insulator that receives a large compression load by supporting an electric conductor, a switching device, or the like, for example, in a substation. In particular, the present invention relates to an insulator apparatus constituted with polymer post insulators and to a method of mounting the same.
2. Description of the Background Art
Hitherto, since post insulators used in a substation not only support an electric conductor but also are structural members constituting a transformer apparatus, a high rigidity is required and also, in a post insulator that supports an opening/closing part of a switching device, a strict position control is required in order to ensure an accurateness in repetition of switching operation. For this reason, insulators made of porcelain being excellent in rigidity have been used as station posts. However, insulators made of porcelain are brittle, and are not durable against a dynamic stress such as generated in a large earthquake or the like. Polymer post insulators are constructed with a solid FRP core for supporting mechanical load such as cantilever and compression, an outer cover having a weather resistance such as a silicone rubber for protecting the FRP core and imparting a suitable leakage distance to the insulator, and metal fitting pieces for connecting the insulator to a supporting structure and to an electric conductor or the like. Since polymer post insulators are excellent in earthquake-proof characteristics and contamination-proof characteristics, polymer post insulators are more and more widely used in recent years as insulators for a substation chiefly in coastal areas that often suffer from earthquake and severe contamination.
While porcelain post insulators are little deformed, the aforementioned polymer post insulators are deformed by being deflected against cantilever load and are deformed by being buckled against compression load. Such deformations increase according as the insulators increase in length, and also the strength decreases according as the insulators increase in length. For this reason, in application of polymer post insulators for substations, insufficient rigidity of the polymer post insulators is a problem particularly for high voltage that requires a long insulation distance.
An object of the present invention is to solve the aforementioned problems of the prior art and to provide a polymer insulator apparatus that can increase the strength in a desired direction and can be applied to a station post for high voltage that requires a long length and to a method of mounting the same.